they're targeting senators, and we have learned president obama as well. we should calling there's always the possibility of fats positives in the initial screening machines. joining me -- pete, first to you, what are we learning about these letters and the possibility of ricin? >> the possibility is the word, andrea. sent from a single person in mississippi, authorities believe they know who has done this. they've questioned that -- and they're waiting to see what the results are on them. ricin is made from castor beans. we've seen this happen in the past, someone will grind up castor beans, put them in an envelope, and that will trip the indicators that are looking for ricin, sort of like the difference between opium and poppies. they come from the same thing, but they're not the same thing. so they have these preliminary tests that -- for the last decade, no mail goes directly to the white house or lots of other government buildings. they have these -- they can't know for certainly until it's cultured, then they'll examine it. there may be more than the